As for a work in a water chamber of a steam generator provided in a nuclear plant, it is desired that the workload of workers is reduced. Therefore, conventionally, there is a technique of performing a work in a water chamber by introducing a water-chamber working apparatus into the water chamber and remote-controlling the water-chamber working apparatus. For example, Patent Literature 1 discloses a remote testing apparatus that performs flaw testing of a number of heat transfer tubes of a steam generator.